A standard sifter bottle intended to hold a supply of fine powder, for instance talcum powder, has a neck or finish to which is fitted a sifter cap. The cap comprises an inner disk part that snaps tightly to the bottle neck and normally does not move once installed, and an outer cup-shaped part engaged with a collar down around the disk with a rim on the bottle neck. The two parts are formed with identical arrays of holes and the outer part can be twisted between an open position with its holes aligned with those of the inner part and a closed position with the arrays of holes offset from each other. In the aligned position powder can be shaken out of the bottle through the cap.
Normally the bottle neck or finish is of cylindrical shape and is formed with a radially outwardly projecting annular ridge that engages under a radially inwardly projecting rim of the outer part. The inner part and neck are also formed with, relative to an axis on which the neck is centered, axially extending groove and ridge formations that interengage to rotationally lock the inner part on the neck so that it does not rotate with the outer part.
The main problem with this type of package is leakage around the edge of the cap. On the one hand the outer part must be mounted loosely enough that it can be turned easily and that it can easily be snapped in place over the neck after filling, and on the other hand it must be tight enough that the powder cannot readily leak out of the joint between the outer part and the neck. One must therefore trade off ease of use and manufacture with potential for leakage so that the bottles and caps must be made to very tight tolerances. As a result they are expensive to manufacture, since if the fit is too tight the cap will not turn and/or the bottle will be crushed as the cap is fitted to it after filling, and when the cap is too loose the resultant package is messy and unmarketable.